This invention relates generally to electromagnetic signal processing and more particularly to a system and method for locating a source of a signal.
Numerous techniques are available for conducting surveillance on targets including foreign military deployments, criminals, or terrorists. Such targets may be optically monitored by ground-based personnel, manned aircraft, unmanned aerial vehicles, or orbiting satellites. Imaging-based methods provide only partial information and are harder to use when the targets are small groups, such as terrorists, who evade detection through concealment in rugged terrain. Targets may also be monitored by detecting audio emissions. Other surveillance methods include monitoring high-frequency signals such as radar, radio or mobile telephone communications, infrared imaging, or motion-detection systems.
Any device that uses electrical power also emits electrical signals. For example devices powered by 50 or 60 Hertz (Hz) electricity, such as televisions, small electrical generators, or automotive accessories, emit electrical signals that are typically disregarded as merely electrical noise. Clandestine forces often operate with a wide range of electronic and electrical equipment in a relatively pristine environment such as mountainous or jungle terrain where there is minimal local electrical background radiation. xe2x80x9cVLF Interferometryxe2x80x9d by Umran S. Inan, available at http://www-star.stanford.edu/xcx9cvlf/interfermetry/VLFinfer. htm (last updated June 2001), discloses an interferometer system that takes active measures to measure a known electromagnetic signal.
According to one embodiment of the invention, a method for locating a source of a signal includes detecting, at a plurality of locations, a near-field signal. The method also includes processing the near-field signal. The method further includes locating a source of the near-field signal based on the processed near-field signal detected at a plurality of locations.
Some embodiments of the invention provide numerous technical advantages. Other embodiments may realize some, none, or all of these advantages. For example, according to one embodiment, a system detects low frequency signals and locates a source for the low frequency signals. In some embodiments, multiple signal detectors are arranged in a three-dimensional array around a low frequency signal source. In addition the low frequency signal detection system utilizes a magnetic loop field antenna small enough to be deployed on an unmanned aerial vehicle or other small device. In some embodiments, a centralized processing station receives signal information from multiple signal detectors, processes the signal information, and locates a source of the low frequency signal.
Other advantages may be readily ascertainable by those skilled in the art from the following FIGURES, description, and claims.